Cable, who is widely expected to replace Farron as Liberal Democract leader, said the issue had led Farron to quit in the aftermath of June’s poll.
LGBT rights and issues were consistently raised with Farron during the General Election.
When he announced he was standing down as party leader, Farron said he felt “remaining faithful to Christ” was incompatible with leading his party.
Cable told Sky’s Sophy Ridge On Sunday that the former leader had done “a great job” in helping the Lib Dems recover from the 2015 election and rebuild its party membership.
But he added: “He did, as he himself acknowledged, not handle that whole issue very well at reconciling his own personal faith with his public positions on gay rights and other issues.
“His position was a perfectly fair one. A lot of people have private views deriving from their religion, but they have to put these to one side when they’re enacting public policy.
“He acknowledged that he hadn’t got that right and that’s why he stood down.”
Cable also said the issue of university tuition fees should be looked at, but he warned Labour’s proposals to scrap fees is a “ridiculously populist programme” which does not stand up to scrutiny.
Any extra funding for education should go to schools, Cable said, adding that universities are the only part of the publicly-funded education system flourishing.
“For goodness sake, some cheap populist gesture killing that off would be a very dangerous and stupid thing to do,” he added.
Cable also said the Lib Dems are committed to holding a second referendum on Brexit and that the UK could remain in the European single market and have greater control over freedom of movement.